Photographic development of silver halide layers



Patented Sept. 10,1940

PATENT OFFICE PHOTOGRAPH IO DEVELOPMENT OF SILVER. HALIDE LAYERS FritzAlbers and Hans Nitze,.Leverkusen-Wiesdorf, Gustav Schaum, Leverkusen-I.G.

Cologne-Niehl, Germany, as-

and Edith Weydc,

Werk,

- signors, by mesne assignments, to General Aniline & Film Corporation,New York, N. Y., a corporation of Delaware No Application May 6, 1939,Serial No. 272,132. In Germany May 10, 1938 6 Claims. Our presentinvention relates to photographic development of silver halide layers.

It has been proposed to incorporate a developing substance in aphotographic silver halide layer before the sensitive layer is exposedand after exposure to develop the image in an alkaline solution, forinstance potassium carbonate or sodium carbonate.

This proposition was for the purpose of simplifying the developingoperation, since only an alkaline solution would be required for thedevelopment. The time needed for the development, as compared with theusual procedure, is not, however, essentially shortened, so that nothingin respect to rapid development is attained by the proposition. A greatdisadvantage of sensitive layers containing the developing substance istheir deterioration during storage.

It is one object of our invention to provide a photographic silverhalide layer containing a developing substance and an organic compoundwhich prevents fog, i. e., a stabilizer.

Another object of this invention is the provision of a photographicsensitive layer which contains a developing substance and in addition tosaid substance a stabilizer in such concentration that the layer isstable in storage and capable of development with caustic alkali withoutproduction of fog.

Further objects of our invention will appear more in detail from thefollowing description.

By a sufiicient addition of organic stabilizerswhich are described forinstance in the U. S. Patents Nos. 1,696,830, dated December 25, 1928,1,758,576 and 1,758,577, dated May 13, 1930, the use of caustic alkalinesolutions which are necessary for rapid development becomes possible,since without these stabilizers there is easily produced by causticalkalies a general grey or dichroic fog in a developed layer alreadycontaining a developing substance. The presence of the organic compoundalso provides the hitherto lacking stability in storage of thephotographic layers containing a developing substance.

For obtaining the desired efiect there may be added, for example, to 1liter of photographic silver halide emulsion either 0.1 gram of2.6-dimercaptol-keto-3.5-diphenylpenthiophene or 1 gram ofnitrobenzimidazole or a mixture of 0.5 gram of nitrobenzimidazole and0.05 gram of 2.6- dimercapto-4-keto-3.5-diphenylpenthiophene.

The development of a photographic silver halide layer of this inventionwith a caustic alkali solution occupies only a few seconds so that it ispossible to develop such a layer in a machine in a very short time, forinstance by applying the developer by means of rollers.

It will be seen that the invention is a combination of three knownexpedients, namely addition of a developing substance to a photographiclayer, 5 simultaneous addition of an organic compound of the kindspecified in a suflicient concentration, and development of the latentimage with caustic alkali. The combination achieves rapid develop mentfree from fog of layers which are stable in 1 storage.

Developing substances suitable for the invention are, for example, theknown organic compounds, such as l-hydroxy-l-methylaminobenzenesulfateand hydroquinone, either alone or in admixture with each other.

The organic stabilizers may be added to the emulsion or any intermediateor protective layer or even to the photographic paper or the surfacingbaryta.

For development there may be used, for example, a caustic soda solutionof 1 per cent strength.

We claim: 25 1. A stable photographic silver halide emulsion containinga developing agent and a small amount of an organic compound capable ofpre venting fog selected from the class consisting of organic compoundscontaining sulfur, capable of forming a stable silver salt with thegroup -SAg and having no higher solubility than silver chloride andorganic compounds containing nitrogen, said emulsion being capable ofdevelopment in caustic alkalis without development of fog.

2. A stable photographic silver halide emulsion containing a developingagent and a small amount of2.6-dimercapto-4-keto-3.5-diphenylpenthiophene.

3. A stable photographic silver halide emulsion 40 containing adeveloping agent and a small amount of nitrobenzimidazole.

4. A stable photographic silver halide emulsion containing a developingagent and a small amount of a mixture of nitrobenzimidazole and 52.6-dimercapto-4-keto-3.5-diphenylpenthiophene.

5. A stable photographic light-sensitive material comprising a silverhalide emulsion containing a developing agent and a small amount of anorganic compound capable of preventing fog selected from the classconsisting of organic compounds containing sulfur, capable of forming astable silver salt with the group -SAg and having no higher solubilitythan silver chloride and organic compounds containing nitrogen, said 55emulsion being capable of development in caustic alkalis withoutdevelopment of fog.

6. The process of developing an exposed photographic silver halideemulsion containing a developing agent and a. small amount oi. anorganic compound capable of preventing 10g, selected from the classconsisting of organic compounds containing sulfur, capable of forming astable silver salt with the group SAg and having no higher solubilitythan silver chloride and organic compounds containing nitrogen, whichcomprises subjecting said emulsion to the action of a solution ofcaustic alkali.

FRITZ ALBERS. HANS NITZE. GUSTAV SCHA'UM. EDITH WEYDE.

